systemctl cat plymouth-start

[Unit]
Description=Show Plymouth Boot Screen
DefaultDependencies=no
Wants=systemd-ask-password-plymouth.path systemd-vconsole-setup.service
After=systemd-vconsole-setup.service systemd-udev-trigger.service systemd-udevd.service
Before=systemd-ask-password-plymouth.service
ConditionKernelCommandLine=!plymouth.enable=0
ConditionVirtualization=!container

[Service]
ExecStart=/sbin/plymouthd --mode=boot --pid-file=/run/plymouth/pid --attach-to-session
ExecStartPost=-/bin/plymouth show-splash
Type=forking
RemainAfterExit=yes
KillMode=none
SendSIGKILL=no

修改 KillMode=mixed

sudo systemctl daemon-reload

参考链接：

https://www.linux.org/threads/solved-how-to-fix-plymouth-start-service-killmode-none-this-is-unsafe-error.41279/